This invention relates generally to a bar clamp of the type used to temporarily clamp together two articles, for example, for gluing, or to hold a workpiece for welding, and more particularly to a quick-action bar clamp wherein the moving jaw can be rapidly advanced or advances in small increments of selectable length. The concept of a bar clamp is old and well-known. In recent years, over-center toggle action handgrips have been incorporated for use in final tightening against the workpiece, for example, in U.S. Pat. Nos. 4,088,313 by Pearson and 4,563,921 by Wallace. A disadvantage in the prior are lies in the fact that adjustment in the moving jaw over a substantial distance is cumbersome and imprecise. Frequently, the moving jaw is entirely disengaged and free to move until the final tightening of an object between the movable and fixed jaws is accomplished. A third hand would be helpful.
What is needed is a bar clamp having a moving jaw which is rapidly movable over both short and long distances to clamp against a workpiece and is operable using one hand with complete control by the operator at all times.
Generally speaking, in accordance with the invention, a bar clamp especially suitable for rapid and precise closure against a workpiece is provided. The clamp includes a fixed jaw and a movable jaw opposing the fixed jaw. The movable jaw connects at one end to a slide bar which is movable to bring the movable jaw toward and away from the fixed jaw. One-way drive means, by operation of a trigger handle grip, releasably engages the slide bar and advances the movable jaw toward the fixed jaw. The one-way drive means is incapable of moving the slide bar and movable jaw away from the fixed jaw. Return motion of the movable jaw is accomplished manually when the one-way drive means is disengaged. A first braking lever which is biased to bind against the slide bar prevents reverse motion of the movable jaw away from the fixed jaw, except when the first lever is disengaged from the slide bar. Thus, for return motion of the jaw, it is necessary that both the one-way drive means and the first braking lever be disengaged. The trigger handle advances the slide bar by driving a second lever which binds against a surface of the slide bar and moves the rod as the second lever moves toward the fixed jaw. The second lever is returned by spring force to its original position after each stroke of the trigger handle, the second lever sliding over the bar surface during its return motion.
Accordingly, it is an object of this invention to provide an improved quick-action bar clamp wherein the moving jaw may be moved over short and long distances rapidly.
Another object of this invention is to provide an improved quick-action bar clamp, wherein the moving jaw may be incrementally and precisely advanced from any position.
A further object of this invention is to provide an improved quick-action bar clamp wherein the moving jaw may be advanced in increments of selectable length for each action of a driving handle.
Yet another object of this invention is to provide an improved quick-action bar clamp wherein the movable jaw does not move its weight when the clamp is in a vertical position.
Still another object of this invention is to provide an improved quick-action bar clamp wherein clamp operation is accomplished with one hand.
Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.
The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts which will be exemplified in the constructions hereinafter set forth, and the scope of the invention will be indicated in the claims.